"While much of the tech world views a two-year-old smartphone as hopelessly obsolete, large swaths of our transportation and military infrastructure, some modern businesses, and even a few computer programmers rely daily on technology that hasn't been updated for decades." Back when I still worked at a hardware and plumbing store - up until about 4-5 years ago - we used MS-DOS cash registers. They are still in use today. If it works, it works.

I work for a company that specialise in maintaining and developing software for legacy systems. These systems are still widely used today, especially in industrial applications such as control systems.

We have customers using equipment from the 1970s, and it's still going strong. The beauty of this hardware is that it is easy to repair. Swapping out burned out resistors or electrolytics on legacy system boards is simple. You just can't do that with today's surface mount, multi layered PCBs.

These systems are still used for the simple reason that it is cheaper to pay a specialist company to maintain the hardware (and software) for the rest of the life of the plant, than it is to develop and commission a replacement system on a modern platform.